A voluntary associa



- E. D. TILLYER OPHTHALMIC LENS Nov. 25, 1930.

2 Sheets-Sheet l Otiglflll Filad Feb. 23, 1922 INVENTOR EDGAR 0. T/LLYERMydd 5 ATTQRNEY E. D. JTILLYER Nov. 25, 1930' OPHTHALMIC LENS- Re. ,8

ori inal Filed Feb. 25, 1922 2 Sheets-Sheet 2 a Y 4 Z 9 5M INVENTOREDGAR D. T/LLYER ATTORNEYS Reissued Nov. 25, 1930 i UNITED STATES PATENTOFFICE EDGAR D. TILLYER, OF SOUTHBRID GE, MASSACHUSETTS, ASSIGNOR TOAMERICAN OPTICAL COMPANY, OF SOUTHBRIDGE, MASSACHUSETTS, A VOLUNTARYASSOCIA- TION OF MASSACHUSETTS OPHTHALMIC LENS Original No. 1,544,612,dated July- 7, 1925, Serial No. 538,563, filed February 23, 1922.Application for reissue filed August 21, 1930. SerialNo. 476,895.

This invention relates to improvements in ophthalmic lenses and hasparticular reference to a novel and improved construction of bifocal ormultifocal lens.

One of the principal objects of the present invention is the provisionof a novel and improved form of two part bifocal or multifocal lens inwhich the circle of the sphere or reading vision portion shall be sodisposed as to best facilitate the use of the portion and to at the sametime eliminate to a very great degree the ump or displacement of theimage as the eye passes over the line of division betweenthe twoportions of the lens.

A further object of the present invention is the provision of a noveland improved manner or process of constructing the lens in question.

A further object of thepresent invention is the provision of a lenswhich shallof itself be novel and produced by a novel process by whichthe relative position of the centers of the near and distance portionare varied as desired Without affecting thegeneral appearance of thelens considered physically as distinguished from optically, and withoutthe ings, audit will be understood that any modifications in thespecific details of construction shown and described 'may be made withinthe scope of the appended claims without def parting from or exceedingthe spirit of my invention.

Figure I is a front view of a pair of glasses embodying the improvement.

Figure II is a front view of the major blank from which the lens isformed.

Figure III is a similar view of the minor disc or segment.

Figure IV is aplan view of a pair of simul taneously constructed lenses.

Figure V is a sectional view of said parts illustrating the method ofconstruction.

.Figure VI. isa similar view of the segment construction, and

Figure VII is a semi-diagrammatic vsectional view through the completedlens illustrating the relationship of the several optical axes and theseveral effects produced.

Figure VIII is a cross sectional view of a slightly modified form ofblank. t

Figure IX is a similar View showing the bifocal side finished.

Figure X is a plan view of shown in Figure IX.

Prior to this invention it has been cus tomary in the construction oftwo part bifocals, as for example, in what is commonly called theKryptok lens, to'make use of a maior portion of one refractive index anda minor portion of a different refractive index, a countersink for theminor portion being formed in the major portion and having its thinnestpointor the point through which the optical axis of the countersinkpasses disposed at the geometrical center of the countersink, Bifocalsof this type when completed have had the center of the reading portiontherefore disposed way down into the reading portion. It is one of thepur-' poses of the invention to obviate the difiiculties present whenthe center is so positioned by providing a construction in which thecenter is near but preferably not on the vthe structure line of divisionbetween the two fields and is i concentrically disposed with respect tothe curved line of division between said fields.

In the drawings there is disclosed a. major portion 1 provided with thecountersink 2 adapted to receive the segment 3 which I suitably securein place either by cement, fusion or the like. In the form shown inFigures I and II it is to be noted that the segment or reading portionis substantially circular in form. Prior to the invention, however, ithas been customary to have this reading portion tapering-to a featheredge around the line of joinder 4 between these fields.- As'distinguished from this, in this invention, however, the segment 3, isformed,

as is shown in Figure III, of a diameter sub stantialLy greater than thecountersink 2 and respect to the normal circular outline of the segment3, the optical center of the convex or countersinkengaging curve of thesegment being disposed as at 6, and the dotted line 5 relatively closelyapproaching this point 6 in the separation. The result is that thesegment thus formed will have a relatively thick edge as at the point 7and ta er to a substantially feather edge at the iametrically oppositepoint 8. At the same time the countersink 2 is formed in tilted relationto the major blank 1, having a thickridge as at 9 and merging outwardinto the surface of the blank as at the point 10. The result of thismanner. of construction is that as is indicated in Figure V, opticalaxis of the ground out countersink will lie on the line 11 or near theedge or shoulder 9 while thesegment mounted in the countersink will forma prismatic member as is most clearly illustrated in connection withFigure VII, the optical axis of said member separately considered beingas along the line 12 connecting the centers of the two sides of thesegment. On account of the difference in index of refraction of the twoglasses, how

ever, the optical axis of the countersink and the optical axis of theincluded segment will both be diflt'erentfromeach other and from theoptical axis of the major portion of the lens. The optical axis of theinserted segment is determined by the line 12 connecting the center 14of curvature of the countersink and rear face of the segment 6 with thecenter 15 of curvature of the front face of the lens, while the opticalaxis of the countersink is determined by the line. 13 connecting thecenter 14 with the center 16 which is the center of curvature of therear'surface. It will be noted by reference to Figure VII that these twooptical axes are verv nearly co-incident and in fact so nearlycorrespond that it is difiicult to distinguish one from the other intheir course through the segment or reading portion of the lens so thatthe optical center of the reading portion is found to be located at thepoint 6 which may be considered as having a right area bounded by thelines 12 and 13 and in upper and lower lenses said center being,-it willbe noticed, near the upper edge of the countersink but preferablyrlghtly space erefrom as well as from the optical axis 17 or thedistance portlonof the lens determined by the centers 15 and 16 and asillustrated in connection with Figure VII. i

In Figures IV, V and VI, there is disclosed another method ofconstructing the lens in which. the results attained and the opticalprinciples involved are identical with those. previously described.- InFigure V it will benoted-that'in this form in place of forming thecountersink 'as an individual proposition, the blanks 1 aresimultaneously and when abraded by the grinding tool or lap 20, the twonecessary depressions or countersinks are formed. The optical axes aredetermined by the combination of the countersink curve and the curve ofthe blank passing through the lenses near the cliff 9 as is clearlyshown in connection with Flgure V. The blank having been thus ground mayeither be retained in the same osition as when ground as is indicated inwhile a single large central button or bifocal segment portion 21 isfused in place or may bereinoved fromthe blank and have individualbuttons applied thereto." The advantage,

so igure VI,

however, of retaining the parts together is that a'single button 21 maybe employed with best satisfaction in .that relation, the heat of fusionemployed being sufficient to sat1s factorily soften the button so thatits edge as at 22 will most firmly and properly fuse or unite with thecliff 9 at the edge of the countersink so as to render the joint betweenthe parts entirely invisible. After the parts have been fused togetherin this paired relation they may then be satisfactorily separated asalong-the dotted line 22 indicated in Figure IV, giving two individualblanks each having a reading portion with its optical center near theupper edge thereof, the lens being formed from two pieces of glassunited by fusion andground to have a smooth and con tinuous curve on thebifocal face thereof. It will, of course, be'noticed by reference tothe, drawings that the fusion of a lar e central button greatlyincreases the thlckness at'the lower edge of the combined blank and itis to be understood that the final grinding of the front curve surfaceissubstantially as I shown in Figure VII cutting down the lower edge ofthe segmfit to merely knife-edge thickness and le ing a relatively muchgreater thickness at the upper edge.

It will be appreciated that there is one, difliculty involved inconnection with the construction of lenses of this type in the higherpower reading additions, this being due to the ncrease in thickness ofthe segment at the point 9 and the consequent necessity of althe blank,the dividing line 4 stopping just short of such edge. The segment 3 isthen fused in position in the usual manner producing a blank such asshown in Figure VIII; Taking this blank as a basis, the lens is thenground with its final prescription curve on the bifocal side with saidcurve swinging down through the segment. 3, removing both the projectingor superfluous portion of said segment and also a portion of thecombined fused segment and major blank toward the outer edge of the lensand a less amount at the central portion of the lens. The semifinishedblank thus produced will have a segment 24 presenting the appearance ofa lentil or double convex lens in face view, in place of a circular orsemi-circular portion, as has been the ordinary bifocal segment known inthe past. This manner of grinding down through the lower portion of thelens, it will be seen, decrease the height 24 of the reading portion orsegment and at the same time decreases its center point thickness, aswill be best understood by a comparison of the length of the lines 25-26and 2728 in Figures VIII and IX, respectively, producing a quite thinlens even with a relatively high power addition and at the same timeproducing a lens having a wire field of vision for reading without thesuperfluous height which is not required for this purpose, andpossessing the extra advantage that the finished lens may be cut out asindicated by the dotted lines in Figure X, so as to leave a small zoneof the distance curve, as at 29, suitable for vision in going up' anddown stairs, or like purposes, where the average bifocal causesannoyance to the wearer.

What is claimed is:

1. A multifocal lens blank having a plurality of sections of glassplaced edge to edge and provided with a continuous countersink overtheir adjacent edges, said countersink having a continuous basalcurvature and an gular shouldered side walls and a segment of glass ofdifferent index of refraction secured in thecountersink.

2. A multifocal lens blank having a plu= rality of sect-ions of glassplaced edge to edge and provided with a continuous countersink overlyingthe adjacent edges of the sections, sa'id countersink having acontinuous basal curvature and angular shouldered side walls and asegment of glass of different refractive index fused in the countersink.

3. A multifocal lens blank having two major portions of glass in edgecontacting relationship and having their geometrical axes parallel toone another, said major portions being provided at their contactingedges with a continuous countersink having a continuous basal curve andshouldered angular side walls, and a segment of different index ofrefraction disposed in the countersink and secured to both majorportions of the blank.

4. The process of producing a multifocal lens blank consisting inmounting a plurality of major sections of glass on av block so that thegeometrical centers will be parallel to one another, forming acontinuous countersink overlying the adjacent edges of the ma jorportions, and having shouldered angular side walls, forming a segment ofglass of.

the contacting edges of the major sections,

grinding a. se ent of glass of different index of refractlon of the sameform and size as the countersink, securing the segment in thecountersink, separating the segment on a line between the edges of themajor portions, and forming each major portion and its segment sectionto a continuous curve.

6. The process of producing a multifocal lens blank consisting inmounting a plurality of major sections of glass'on a block insubstantially edge. contacting relationship and with their geometricalcenters parallel to one another, forming a continuous countersink withshouldered angular side walls overlying the. contacting edges ofthe'major sections, forming a grinding segment of glass of differentindex of refraction of the same form and size as the countersink,securing the segment in the countersink, separating the segment on aline between the edges of the major portions, forming each major portionand its segment section to a continuous curve, and shaping the secondside to a prescription curve.

7. A,Inultifocal lens comprising a major portion for distance vision,and a minor portion for near vision inserted in the major portion, bothportions being finished to one 0on tinuous curve-the minor portionhaving a thin lower edge blended into the finished curve, and having athick shouldered'upper edge lying below the optical center of the majorportion and above the. optical center of the minor portion.'

8. A multifocal lens comprising a major portion of glass of one index ofrefraction, and a minor portion of glass of a different index ofrefraction inserted in the major portion and both portions finished toone continuous curve, said minor portion tapering from a thick upperedge to a feather edge at its lowest .point and the optical center ofthe minor portion being located near and below the thick edge at a pointwhere a line drawn thru the center of curvature of the front and rearsurfaces of the minor portion In testnnon} whereof I hev e afiixed mysignature.

EDGAR D. TILLER lib-

